The Chronic Dev Team has just published a Mac OS X version of Absinthe on their blog, unfortunately a Windows version is not available at this time. Absinthe for Mac OS X only works with iPhone 4S and iPad 2, but for iPhone 4S you must have iOS 5.0/5.0.1 installed and for iPad 2 you must have iOS 5.0.1 installed. If you need to jailbreak your iPhone 4S, then do not update to iOS 5.0.1 at the moment because you may not be able to unlock it in the future.
You can download Absinthe for Mac OS X available here.
UPDATE: Here you can find a jailbreak tutorial.
